The present invention relates generally to the formation of conductive films on insulating surfaces. More particularly, it relates to formation of conductive tungsten metal films on insulating surfaces of silicon dioxide.
There is a continuous trend in the development of solid state circuitry to reduce the dimensions of the devices on insulating surfaces and in this way to increase the speed of operation. As the dimensions of devices on surfaces such as silicon wafers continue to shrink and as the speed of the operation of the circuitry continues to increase, a need is recognized for improvements in the formation of conductive films and in the production of higher conductivity films. Further, there is a recognized need for improved coverage of the topographic steps of the surfaces on which the devices are formed in order to interconnect the devices. Chemical vapor deposition of tungsten on such surfaces has been identified as a process which may be suitable for use in connection with the development and production of solid state circuitry.
However, a problem has been recognized in attempting to grow a uniform adherent film of tungsten on a surface such as a silicon dioxide surface. Where vapor deposition methods are employed, the problem relates particularly to the nucleating and growing of a uniform and adherent film. Tungsten film does not readily or reliably deposit directly onto silicon dioxide surface. To the extent that it does deposit it does not adhere to the silicon dioxide surface. This is so whether the mode of deposition is thermal vapor deposition or chemical vaporization.
There are other uses of thin films of tungsten in industry although the function and attributes of these films is not known or is not clear. For example Hewlett-Packard employs an unspecified layer under a chemically vapor deposited tungsten layer in some of their devices. This layer may be to promote adhesion of the tungsten layer. Details are not known.
Another example is the deposit of a thin layer of tungsten silicide, WSi.sub.2, under the chemical vapor deposited tungsten layers of devices of a corporation trading under the name Genus. The attributes, properties and functions of this film are not known.
Intel Corp., as well as other corporations, are understood to deposit chemical vapor deposited tungsten on thick polycrystalline lines of their devices to enhance conductivity. No detailed information is available to applicant relating to such films.
Applicant is not aware of any other technology or prior art in which the objective is to replace a thin patterned deposit on a receiving surface with tungsten.